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Ask me anything physics related! I'll keep to laymans terms and no math if possible. :-) Choose from cosmology to string theory. What about the Universe doesnt make sense? Black holes? Quantum electrodynamics? Planetary formation? M-Theory and Branes? Higgs Boson? Quantum tunneling?
Lets see where the conversation goes! :-) And if you are reading a question yet to be answered and you know the answer, chime in too! Lets try to make this the longest Science thread ever on city-data.
Is the universe bounded or by definition, does it extend for infinity in three dimensions?
A fun start! 3 dimensions must mean you arent including our 4th dimension, that of time. And there may be more dimensions if you subscribe to most of string theory.
The Universe as we know it now will continue to expand, at least until all particles decay and we're back to nothing.
Space exists where matter is present. There's no "edge" to the Universe (and even if there was, we cant ever reach it since its expanding faster than the speed of light).
If our Universe is one "bubble" out of a larger spacial area, then there's even a chance that we may "run into" another Universe. Think of a bubble bath where we're one bubble, and other Universes are other bubbles. Sometimes they touch and interact! Wouldn't that be an interesting situation?
Now usually when we say "Universe" we mean our observable Universe. If the Universe is isotropic, then we can only see it as a bubble as far as light has traveled to us, which is where we say its 14 billion years old. But someone looking out a few billion light years out will see something different. Now the actual "entire" Universe could be 1,000,000,000,000,000,000,000,000 times larger than our own observable Universe. And everything we cant see, should be expanding, too.
So for now, the best information we have provides an quick answer to your question -- "Yes!".
That question is ambiguous. I remember this from a few years ago when the question hit some Internet forums. Short answer: 2, or 288. The actual question should be written as (48/2)(9+3) or 48/(2(9+3)).
That question is ambiguous. I remember this from a few years ago when the question hit some Internet forums. Short answer: 2, or 288. The actual question should be written as (48/2)(9+3) or 48/(2(9+3)).
If there are an infinite number of suns and planets and time goes back to infinity, then this is the infiniteth time this post has been written. Everything you did today, drank a cup of coffee, thought about the football game, dropped your shoe in exactly that same place in the closet has been done before an infinite number of times. Since the number of planets is infinite and time is infinite, then every possible combination of events (position and states of matter in time) has been repeated an infinite number of times.
Either that or Adam and Eve were placed in a garden and they talked to a snake.
Does the topology of the common view of the universe depend upon Euclidean geometry?
Why is a small infinity smaller than a large infinity?
If two parallel lines extended past the beginning of the universe, would they meet in the singularity?
If Steve Hawkins was in a box and we couldn't see him, would he be dead or alive?
If the answer to everything is 42, why do we need a towel?
If there is no matter in the interstellar voids, what is it that crosses them to show us the light from stars?
If the Higgs Boson gives mass, why do we need a Pope?
How do we know that what happened before the big bang wasn't the real universe?
If the speed of light in a vacuum is finite and defined, and star going away only exhibit a red-shift and those coming towards us a blue-shift, is the existence of unseen light in interstellar space real, or is the light we see merely an expression of probability?
When the "mass" in a nuclear reaction is converted to energy, is there an equal amount of "energy" that gets converted to mass?
Are the nodal points in electron orbits the only real cause of the variety of atomic properties beyond "mass"?
Why is helium considered a starter element when hydrogen is much simpler?
If electromagnetic radiation passes through the gaps between molecules, what gives lead the upper hand in stopping it? It still has plenty of unoccupied space.
Ask me anything physics related! I'll keep to laymans terms and no math if possible. :-) Choose from cosmology to string theory. What about the Universe doesnt make sense? Black holes? Quantum electrodynamics? Planetary formation? M-Theory and Branes? Higgs Boson? Quantum tunneling?
Lets see where the conversation goes! :-) And if you are reading a question yet to be answered and you know the answer, chime in too! Lets try to make this the longest Science thread ever on city-data.
Ben the Physicist
I think Alpha Centauri is the closest star system to Earth (about 4 light years), and they've discovered planets recently. Say we develop a fast enough engine to send a probe there. Even if a probe goes super fast and takes it only a few years to get there and back, due to relativity how long would it take in our view? Could we even send a probe to take pictures and come back in our lifetime if it left today?
If our Universe is one "bubble" out of a larger spacial area, then there's even a chance that we may "run into" another Universe. Think of a bubble bath where we're one bubble, and other Universes are other bubbles. Sometimes they touch and interact! Wouldn't that be an interesting situation?
Depends on how you look at it. If the inflationary phase of the "whole" universe never stopped, and the universe we see is just one bubble of many that "dropped out" of the inflation when that area decayed to a lower energy state, there is no way any of them would ever "run into" each other or be causally linked in any way; they would be moving away from each other at an ungodly high speed.
If there are an infinite number of suns and planets and time goes back to infinity, then this is the infiniteth time this post has been written. Everything you did today, drank a cup of coffee, thought about the football game, dropped your shoe in exactly that same place in the closet has been done before an infinite number of times. Since the number of planets is infinite and time is infinite, then every possible combination of events (position and states of matter in time) has been repeated an infinite number of times.
Either that or Adam and Eve were placed in a garden and they talked to a snake.
This is sort of right. If the universe is infinite in spatial extent and both homogenous (has roughly the same matter content everywhere) and isotropic (looks the same in every direction - not just its matter content, but how physical laws apply to its functioning), then every possible configuration of particles has, is, or will happen somewhere. And since the number of ways particles can be arranged is finite, the 'pattern' of the universe will start repeating eventually. It is truly possible that there are infinite copies of myself writing this post "right now" (I put right now in quotes because it is impossible to say two events, even identical events, are both occurring "right now" when they are an unimaginable distance apart).
The only error in your post is that time is not infinite. Time began when the Big Bang occurred.
Think about this: If we assume that new universes can be created, and that such a process can occur eternally, it is only a matter of 'time' until a universe with the same physical laws and constants as this one is created. And since already know that the existence of humanity is possible in such a universe, that new universe will contain humans.
I love physical cosmology (it is my favorite scientific discipline) and will also try to answer any non-math related questions about it.
Last edited by Lunar Delta; 09-02-2013 at 10:52 PM..
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